Study of the Irreversibility Line of GdBa 2Cu 3 O 7 − δ Added with Nanosized Ferrite CoFe 2 O 4

Abstract

CoFe 2 O 4 ) x GdBa 2 Cu 3 O 7−δ superconducting samples were synthesized using a conventional solid-state reaction technique with 0 ≤ x ≤ 0.1 wt%. Characterization of the prepared samples was carried out using X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The effect of adding CoFe 2 O 4 to the Gd-123 phase, which acts as a flux pinning center, was investigated by measuring the ac magnetic susceptibility at different applied dc magnetic fields. Both the superconducting transition temperature T c and the critical current density J c increased up to x = 0.01 wt%, and then, they decreased with further increase in x. The temperature dependence of the irreversibility line was investigated by the logarithmic plot of the irreversibility field H irr versus (1 − T irr /T c (0)). This plot shows a crossover at a field of 1000 Oe, indicating 3D to 2D flux creep fluctuations. Furthermore, the H irr -T curves are well fitted according to a theoretical model proposed by Matsushita, based on the depinning mechanism caused by thermally activated flux creep.

Effect of Size, Shape and Environment on the Optical Response of Metallic Nanoparticles

“…Nanomaterials are macroscopic systems but constructed and organized from elementary bricks of nanometric dimensions known as nanoparticles. They have many fields of application, in the fields of optics [1,2], magnetism [3,4], electronics [5,6], telecommunications [7,8], superconductors [9,10], chemical catalysis [11] or biological marking [12].…”